In the case of charging of traffic from user terminals, and in particular in the case of charging of traffic from Packet Switched, PS, data mobile terminals which are roaming in a Visited Public Land Mobile Network, a VPLMN, the traffic either passes the Home Public Land Mobile Network, the HPLMN, or the Home Operator relies on the Visited Operator to generate the Charging Data Records, the CDRs, to be used by the Home Operator for billing. The Visited Network generates a traffic counting record comprising the traffic counting information from the Visited Network. The traffic counting record is subsequently sent to the Home Network.
In present 3GPP mobile Packet Switched networks, it is possible to use both Internet Protocol version 4, IPv4, and version 6, IPv6, to carry packets containing user traffic.
Besides obtaining PS access service in an operator's Home network, it is also possible establish a connection to the Home Operator using a Visited Operator's access network, i.e. roaming. To settle the costs for roaming users between the Home Operator and the Visited Operator, information on transport usage is sent from the Visited Operator to the Home network by means of billing records also known as Charging Data Records, CDRs. The 3GPP specification TS 32.298 describes the format of the CDRs. Depending on which IP version traffic that is used, the CDRs differ in Information Elements, IEs, for example IEs which state the servedPDPAddress/servedPDPPDNAddress and pdpType/pdpPDNType
Roaming users are billed by the Home operator. When a PS data user is roaming, the SGSN/SGW (Serving Gateway) in the VPLMN will perform traffic measurements and count the amount of traffic that is handled. The traffic reports are sent to the Home Operator as CDRs, or so called TAP (Transferred Account Procedure) records which are derived from the CDRs, for accounting between the operators. In a solution in which the traffic also passes the HPLMN via a GGSN or a Packet Data Gateway, a PGW, in the Home Operator's network, the Home Operator generates his own CDRs, and there is a double check in the Home Operator's GGSN/PGW that the traffic charges that the Visited Operator claims from the Home Operator (and also the billing of the user) are correct.
In the case of a roaming user who uses IPv6 traffic in a VPLMN, the CDR generating node in the VPLMN will generate CDRs according to the CDR format for IPv6 traffic. The billing system in the VPLMN which receives such IPv6 CDRs from the CDR generating node in the VPLMN is capable of handling IPv4 CDRs, but may not be able to handle IPv6 CDRs. In such a case, when the VPLMNs billing system receives CDRs it does not recognize, in this case IPv6 CDRs, those CDRs cannot be handled within the billing system, and thus the traffic volume represented by those CDRs cannot be billed, and the revenue will be lost unless handled manually.